Quick turn fastener

ABSTRACT

A fastener for use in connection with a tubular boss has a shaft with at least one rib along the length thereof and at least one thread segment extending at least partially around the shaft. The shaft is inserted into the boss in first position, and rotated to a second position wherein the at least one thread segment engages at least one column formed in the tubular boss. The shaft can be integrally formed with a first molded part to be fastened to a second molded part with an integrally formed tubular boss. Various locking features for locking the shaft in the boss are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. application Ser. No.13/696,609, filed Nov. 7, 2012, now U.S. Pat. No. ______, issued on______, which is the United States national stage filing ofInternational Application Number PCT/US11/37761, filed May 24, 2011,which claims the benefit of and priority to U.S. Provisional PatentApplication Ser. No. 61/347,671, filed on May 24, 2010, which isincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to fasteners. In particular, thepresent invention relates to a quick turn fastener for use with a moldedor extruded tubular boss.

The fastener of the present invention is particularly useful forattaching to a plastic molded or extruded part. Existing fasteners foruse with plastic molded materials are generally intended for attachmentto flat panels, and require a flat panel or a through-hole in order towork. Examples include existing quarter-turn, “Christmas tree” andsnap-fit style fasteners. The existing fasteners work reasonably wellfor their intended applications, but are not practical for attachment tomolded parts where no flat panel or through-hole is available.

A tubular boss is a very desirable attachment feature for injectionmolded parts. Metal screws are commonly used to directly fasten to thetubular boss, forming threads on the inside. Thread forming metal screwscan provide a connection with a high resistance to pull out, but thismay not be required by the design and it may be more important to have atool-free or quick assembly without the need for screw-driving equipmentor tools. Metal screws also have the potential to corrode, which can bevery undesirable. Non-threaded tubular bosses are simple to injectionmold or extrude. They allow the use of blind holes for an air tightbarrier, and they offer substantial diameter to length support forbending strength and alignment of attached parts. Unfortunately, no goodmethod exists for attaching a plastic fastener directly to a simpletubular boss using prior art fasteners. As a result, metal screwscontinue to be used due to a lack of alternatives, which allowscorrosion and adds costs, complexity and assembly time.

Thread forming using plastic screws in place of metal has beenattempted, since thread forming is possible if the male thread is madefrom a material that is higher strength than the tubular boss. Oneexample is using a male screw made of 30% glass-filled nylon to threadform into a much softer polypropylene tubular boss. However, preventingstripped threads becomes more difficult due to generated heat that cansoften the threads. There is also increased risk of vibration loosening,since maintaining screw clamp load is more problematic with plasticmaterial used for both the screw thread and tubular boss. A fullythreaded tubular boss does not do much to avoid these potential issuesand ‘unscrewing molds’ add considerable cost and complexity to mold toolconstruction. Assembly time is still slow and requires tools, comparedto snap fit and quarter-turn style fasteners used in flat panels. Crossthreading, axial alignment to the tubular boss, and achieving a specificrotational position after assembly are all difficult to control.

A complete injection moldable fastening system is desirable, in whichthe fastener is incorporated directly into the injection molded productdesired to be fastened, to speed assembly and eliminate screws. A fewexamples are wire guides, stand-offs and various stud designs but manyother possibilities exist.

Accordingly, a need exists for an improved quick turn fastener andfastening method that solves these and other deficiencies in the priorart. Of course, the present invention is not limited to plastics, may beused in softer metals and a multitude of situations where similarperformance capabilities are required.

SUMMARY OF THE INVENTION

The present invention provides a fastener and fastening method that iscost effective, provides improved functionality, and eliminates certainof the deficiencies inherent in existing designs.

In one embodiment of the present invention, a fastening assemblyincludes a shaft that mates with a tubular boss. The shaft has at leastone rib along its length and at least one thread segment extending atleast partially around the shaft from the at least one rib. The tubularboss has a cylindrical opening with at least one column disposedtherein. The shaft is inserted into the tubular boss in a first positionand rotated, preferably a quarter-turn, into a second position such thatthe thread segment engages the columns. Various locking features can beused to lock the shaft in the boss as needed for a particularapplication and function without the need for clamping force.

Another embodiment of the present invention is a fastener for use inconnection with a molded tubular boss having a cylindrical opening andat least one column formed therein. The fastener includes a shaftconfigured for insertion into the tubular boss, at least one rib formedalong the length of the shaft, and at least one thread segment extendingat least partially around the shaft from the at least one rib. The shaftcan be inserted into the boss in a first position and rotated to asecond position such that the at least one threaded segment engages theat least one column. Preferably, engagement between the shaft and theboss is achieved via thread forming, wherein the shaft is formed from aninjection molded plastic or die-cast metal material of higher strengththan that of the tubular boss to allow the at least one thread segmentto pierce the at least one column. Alternatively, the tubular boss couldinclude internal thread segments formed within the cylindrical openingto engage the at least one threaded segment of the shaft.

A method for attaching a first molded part to a second molded part isalso contemplated by the present invention. The method includes thesteps of: providing a shaft in accordance with the present inventionintegrally formed on the first molded part; providing a tubular boss inaccordance with the present invention integrally formed on the secondmolded part; inserting the shaft into the tubular boss in a firstposition; and rotating the shaft to a second position, wherein the atleast one threaded segment engages the at least one column. The methodcan also include the step of locking the shaft in the rotated position.

Various embodiments of the present invention overcome many of thedisadvantages associated with the prior art. Alignment to the boss maybe maintained because the shaft can be fully inserted into the tubularboss before rotating. Cross-threading can be avoided, and concentricalignment is achieved. Rotational position can be controlled by thecolumns inside the tubular boss. No drive torque, strip torque or speedcontrols are needed because the product can be rotated to a dead stopwhen the columns meet the ribs and no significant heat results with thequarter-turn rotation. The locking features, when used, are independentof clamping force and material relaxation, which avoid vibrationloosening. The assembly time is very fast, and no tools or screw-drivingequipment are needed. All of these features of the present inventionrepresent a significant improvement over prior art fasteners andfastening methods.

While certain possible applications and advantages of the presentinvention have been described herein, many other applications arepossible and references to use in connection with a particularapplication should not be deemed to limit the uses of the presentinvention. The terms used herein should not be interpreted as beinglimited to specific forms, shapes, or compositions. Rather, the partsmay have a wide variety of shapes and forms and may be composed of awide variety of materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a fastening assemblyof the present invention;

FIG. 2 is a perspective view of another embodiment of a fasteningassembly of the present invention, showing the fastener turned in afirst position;

FIG. 3 is a perspective view of the fastening assembly of FIG. 2,showing the fastener turned in a second position;

FIG. 4 is a perspective view of one embodiment of a fastener used inconnection with the present invention;

FIG. 5 is a perspective view of one embodiment of a tubular boss used inconnection with the present invention;

FIG. 6 is a perspective view of another embodiment of a tubular bossused in connection with the present invention;

FIG. 7 is a perspective view of another embodiment of a fasteningassembly according to the present invention, showing one embodiment of alocking feature;

FIG. 8 is an exploded perspective view of another embodiment of afastening assembly of the present invention;

FIG. 9 is a perspective view of another embodiment of a fastener used inconnection with the present invention;

FIG. 10 is a top plan view of one embodiment of the fastening assemblyof the present invention, showing the fastener turned in a firstposition;

FIG. 11 is a top plan view of the fastening assembly of FIG. 10, showingthe fastener turned in a second position;

FIG. 12 is a bottom plan view of the fastening assembly of FIG. 10,showing the fastener turned in the first position;

FIG. 13 is a bottom plan view of the fastening assembly of FIG. 11,showing the fastener turned in the second position;

FIG. 14 is a perspective view of one embodiment of a fastening assemblyof the present invention incorporated into a collar stud arrangement sothat it may be used as an adjustable stand-off;

FIG. 15 is a perspective view of another embodiment of a tubular boss ofthe present invention, illustrating the use of internal threads;

FIG. 16 is a perspective view of another embodiment of a fastener of thepresent invention incorporated into a wire guide and illustrating theuse of alternate side coring as a simplified means of mold toolconstruction; and

FIG. 17 is a perspective view of another embodiment of a fastener of thepresent invention, illustrating the use of non-helical threads andthread relief.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the fastening assembly 50 includes afastener 10 that mates with a tubular boss 20. The fastener 10 includesa shaft 12 with at least one rib 14 along its length and at least onethread segment 16 extending around the shaft 12 from the rib 14. In theembodiments shown, the shaft 12 includes two ribs 14 and two threadsegments 16 separated by channel openings 18, although othercombinations and numbers of ribs, thread segments and channel openingscould be used. The thread segments 16 can be formed in a helical patternas shown in FIGS. 4, 8, 9 and 16 or a non-helical pattern as shown inFIG. 17. The shaft 12 is intended to be incorporated into a molded partsuch as the parts shown at least in FIGS. 16 and 17. For simplicity ofillustration, FIGS. 4 and 8-9 show the shaft 12 molded along with asimple flange 28 and turning knob 30.

One embodiment of the tubular boss 20 includes a cylindrical opening 22and at least one column 24. The use of two columns 24 as shown in thedrawings has been found quite effective for many applications. Inanother embodiment, the tubular boss 20 has internal thread segments 38as shown in FIG. 15. The internal thread segments 38 can be formed usingless expensive ‘collapsing’ core pins instead of unscrewing mechanisms.The boss 20 is preferably molded into the part onto which another partwill be fastened, or vice versa. The cylindrical opening 22 of the boss20 can be either a through hole or a blind hole, and the boss 20 can beeither molded such that it extends into the part, as shown in FIG. 1 forexample, or out of the part as shown in FIGS. 2 and 3.

The shaft 12 is inserted into the cylindrical opening 22 of the boss 20with the channel openings 18 aligned with the channels or columns 24.The shaft 12 is then rotated or turned inside the boss 20 such that thethread segments 16 engage the columns 24 on the inside of the boss 20.The use of a quarter turn to engage the shaft 12 to the boss 20 isparticularly effective and advantageous for many applications. Tofacilitate engagement of the thread segments 16 with the columns 24, thethread segments 16 can be formed from a plastic material of higherstrength than that of the plastic material used for the tubular boss 20.When a helical thread pattern is used, an additional clamping force isgenerated between the boss 20 and shaft 12, which is useful in manyapplications. The use of a non-helical thread pattern as shown in FIG.17 creates the option of first positioning the shaft 12 into the tubularboss 20 at a desired depth, which may be at any point along the lengthof the shaft 12, and then rotating to the locking position. This wouldcreate an adjustable stand-off, as shown in FIG. 14, which is in itselfa desirable feature in some designs.

A variety of locking features can be used in connection with thefastener 10 of the present invention. FIG. 7 shows one example of alocking feature, wherein the flange 28 of the shaft 12 includes a tab 34that interacts with a ramp 32 on the boss 20. The tab 34 can easily passover the ramp 32 as the knob 30 is turned clockwise to engage the shaft12 to the boss, but the tab 34 cannot pass back over the ramp 32 if theknob 30 is turned in the counter-clockwise direction. Another lockingfeature is shown in FIGS. 8, 9, 12 and 13 as an “S” shaped flex tab 40.Once the shaft 12 is rotated a full quarter turn, the flex tab 40 seatsin between the columns 24 and prevents counter-rotation of the shaft 12.A thread relief 52 as shown in FIG. 17 can also be used as a mildlocking feature.

The shaft 12 of the fastener 10 can be incorporated into a variety ofmolded parts to facilitate attachment to other parts. For example, FIG.17 shows a shaft 12 of the present invention incorporated into a collarstud arrangement with a hex collar 56, panel 58 as seen in FIG. 14, andthread 60 for use as an adjustable stand-off and FIG. 16 shows a shaft12 of the present invention incorporated into a wire guide 54. The shaft12 of the present invention can also be used in connection with avehicle lamp assembly fastener, where a shaft 12 of the presentinvention is molded into the stud of the lamp assembly fastener and atubular boss 20 is molded into the lamp assembly. These examples are afew of many possible applications for the fastener of the presentinvention.

Many different materials can be used for the various components of thepresent invention, including metals, composites and plastics. It hasbeen found cost effective to manufacture the majority of the componentsout of injection-molded plastic or plastic composite materials. Whenusing an injection molding process, certain parts can be molded using asimplified mold tool design, wherein all part features are formedwithout the need for core pins. For example, a fastener made via the useof alternate side coring 62 as a simplified means of mold toolconstruction is shown in FIG. 16.

The fastening assembly can also be easily altered to accommodate variousdesign and molding requirements that are difficult to meet usingconventional threaded fasteners. The fastener 10 and tubular boss 20could be significantly tapered or “drafted” by, for example, fivedegrees or more, if this becomes advantageous for design or moldingreasons. Conventional threads can only have a very mild taper, so arevery limited in that regard. The pitch between the threads of thefastener 10 of the present invention can be large for deep engagement,but the helix or thread slope can be mild for optimum vibrationresistance, whereas conventional threads must tradeoff between the twofeatures.

The fastener of the present invention may have other applications asidefrom those specifically described herein. The fastener has applicationsin a number of different industries and would be useful in allapplications where attachment to a tubular boss is desirable. Althoughthe invention has been herein shown and described in what is perceivedto be the most practical and preferred embodiments, it is to beunderstood that the invention is not intended to be limited to thespecific embodiments set forth above. Rather, it is recognized thatmodifications may be made by one of skill in the art of the inventionwithout departing from the spirit or intent of the invention and,therefore, the invention is to be taken as including all reasonableequivalents to the subject matter of the appended claims and thedescription of the invention herein.

What is claimed is:
 1. A fastener assembly comprising: a shaft having atleast one rib along its length and at least one thread segment extendingat least partially around the shaft from the at least one rib; aplurality of thread forming threads extending from the at least onethread segment; a tubular boss having a cylindrical opening with atleast one column disposed therein; and wherein the shaft is insertedinto the tubular boss in a first position and rotated into a secondposition such that the at least one thread segment engages the at leastone column via some of the plurality of thread forming threads.
 2. Thefastener of claim 1, wherein the shaft includes at least one channelopening.
 3. The fastener of claim 1, further comprising a lockingfeature.
 4. The fastener of claim 3, wherein the locking feature is aflex tab formed at an end of the shaft.
 5. The fastener of claim 3,wherein the locking feature is a tab and ramp.
 6. The fastener of claim3, wherein the locking feature is a thread relief formed in theplurality of thread forming threads.
 7. The fastener of claim 1, whereinthe plurality of thread forming threads are in a helical pattern.
 8. Thefastener of claim 1, wherein the plurality of thread forming threads arein a non-helical pattern.
 9. The fastener of claim 1, wherein the shaftis integrally formed with a first molded part and the tubular boss isintegrally formed with a second molded part.
 10. The fastener of claim9, wherein the first molded part is a stud of a lamp assembly fastenerand the second molded part is a lamp assembly.
 11. The fastener of claim1, wherein the plurality of thread forming threads are made of a firstmaterial and the at least one column is made from a second material andthe first materials is harder than the second material.
 12. The fastenerof claim 1, wherein at least one of the shaft and cylindrical opening istapered at least five degrees.
 13. A method for attaching a first moldedpart to a second molded part, the method comprising the steps of:providing a shaft integrally formed on the first molded part, the shaftincluding at least one rib along its length and at least one threadsegment extending at least partially around the shaft from the at leastone rib; providing a tubular boss integrally formed on the second moldedpart, the tubular boss having a cylindrical opening and at least oneinitially unthreaded column disposed therein; inserting the shaft intothe tubular boss in a first position; rotating the shaft to a secondposition, wherein the at least one thread segment forms threads in theat least one initially unthreaded column to engage the at least onethread segment to the at least one initially unthreaded column.
 14. Thefastener of claim 13, wherein the shaft includes at least one channelopening.
 15. The fastener of claim 13, wherein the shaft has a flex tabat an end and the tubular boss has first and second initially unthreadedcolumns and rotating the shaft to a second position, wherein the flextab is seated between the first and second initially unthreaded columns.16. The fastener of claim 13, wherein the shaft has a flange with a taband the tubular boss has a ramp and rotating the shaft to a secondposition, wherein the tab is positioned behind the ramp.
 17. Thefastener of claim 13, wherein the at least one thread segment includes athread relief and rotating the shaft to a second position, wherein thethread relief is seated behind the at least one initially unthreadedcolumn.
 18. The fastener of claim 13, wherein the threads of the atleast one thread segment are formed in a helical pattern.
 19. Thefastener of claim 13, wherein the threads of the at least one threadsegment are formed in a non-helical pattern and before rotating theshaft to a second position, positioning the shaft in the tubular boss toa desired depth.
 20. The fastener of claim 13, wherein the shaft isintegrally formed with a first molded part and the tubular boss isintegrally formed with a second molded part.